Confidence was shattered last year when energy reform withdrew power price support for all wind power online before 2007 — 30% of Spain's 23GW total — breaking a state-backed 20-year support commitment.

If the sector is to install a further 5GW to 2020, as set in the recently completed national energy plan, confidence will require "something like a state energy pact" to "depoliticise" the sector, Tafall said.

In April, Spain's industry ministry issued a draft royal decree detailing plans for a 500MW wind power auction.

The AEE said the 500MW total was acknowledgement by the government that it needs more wind, but said it would fail to meet 2020 targets.

AEE also warned projects involved in this auction could be subject to an economic change in 2019, due to Spanish law, meaning developers would be unsure of project profitability beyond that date.

Last year, Spain added just 28MW of onshore wind to its total capacity — most of which was installed in a pre-2008 boom.